1. Field of the Invention
The present invention relates to a solid-state imaging device, a method of producing the same, and a camera. In particular, the present invention relates to a solid-state imaging device including a photoelectric conversion portion that receives light on a light-receiving surface and that photoelectrically converts the light received on the light-receiving surface to generate a signal charge and an optical waveguide that guides light to the light-receiving surface, a method of producing the same, and a camera including the solid-state imaging device.
2. Description of the Related Art
Cameras such as a digital video camera and a digital still camera include a solid-state imaging device. For example, such cameras include a complementary metal oxide semiconductor (CMOS) image sensor or a charge-coupled device (CCD) image sensor as a solid-state imaging device.
In a solid-state imaging device, an imaging region where a plurality of pixels are provided is disposed on a surface of a semiconductor substrate. In this imaging region, a plurality of photoelectric conversion portions that receive light from an object image and that photoelectrically convert the received light to generate signal charges are provided so as to correspond to the plurality of pixels. For example, photodiodes are provided as the photoelectric conversion portions.
In such a solid-state imaging device, with an increase in the number of pixels, the cell size of each pixel has been reduced. As a result, the amount of light received per pixel may decrease, resulting in a decrease in the sensitivity.
Consequently, in order to increase the light-focusing efficiency to improve the sensitivity, an optical waveguide is formed for each pixel.
Specifically, the optical waveguide is composed of an optical material having a high refractive index and includes a core portion that guides light. A cladding portion having a lower refractive index than that of the core portion is provided around the core portion. Consequently, in the optical waveguide, incident light can be totally reflected at the interface between the core portion and the cladding portion. Accordingly, by providing the optical waveguide, the light-focusing efficiency can be increased to improve the sensitivity. For example, the core portion is formed of an organic resin material (refer to, for example, Japanese Unexamined Patent Application Publication Nos. 2006-222270 and 2006-156799).
In addition, in such a solid-state imaging device, a color filter is provided on the core portion of the optical waveguide. In the color filter, light is colored and emitted to the optical waveguide. This color filter is formed by using a photolithography technique.
Specifically, for example, the color filter is formed by applying a photosensitive resin film containing a dye, and then sequentially performing an exposure process and a development process on the photosensitive resin film.